Say "skipped" in scan's warnings for skipped paths (closes #170)

A warning for a path the summary counts as skipped now reads
`scan: skipped PATH (REASON)`, naming the path once. This covers
unreadable directories, failed lstats, failed reads and dropped
operands. Each path of a hard-linked file that cannot be read gets its
own line, since each is counted. Lines for paths left out on purpose
(`--exclude`, default excludes, filesystems that are not persistent)
now read `scan: left out PATH (...)`, so a search for `scan: skipped`
finds only the counted paths.

Model: opus-5-5

README.md

@@ -253,9 +253,8 @@ In order:
    `trees` check only that each copy they name still exists, and leave out a
    copy that is gone. `scan` is built to run from `cron`. The reports run at any
    time, against what the database holds.
-4. **Keep the streams apart.** stdout holds only what was asked for:
-   machine-readable data, or help. Everything else for a human reader, such as
-   progress and warnings, goes to stderr.
+4. **Keep the streams apart.** Everything on stdout is machine-readable data.
+   Everything for a human reader, such as progress and warnings, goes to stderr.
 
 ### Subcommands
 
@@ -325,13 +324,12 @@ The reference below is also the program's specification.
   "Operands").
 - `--version`, `-v` prints `sfdupes VERSION` (see "Install") to stdout and
   exits 0. It writes nothing to stderr.
-- `--help`, `-h`, alone or after a subcommand, prints the help text to stdout
-  and exits 0. It writes nothing to stderr. `sfdupes help` and
-  `sfdupes help COMMAND` do the same. The help of `sfdupes` and of `scan` names
-  the database. The help of `report`, `trees`, `info` and `dwim` says what each
-  prints. `sfdupes scan --help` and `sfdupes dwim --help` also list the default
-  excludes of the system they run on, and the filesystem types the walk never
-  records anything on.
+- `--help`, `-h`, alone or after a subcommand, prints the help text to stderr
+  and exits 0. It writes nothing to stdout. The help of `sfdupes` and of `scan`
+  names the database. The help of `report`, `trees`, `info` and `dwim` says what
+  each prints. `sfdupes scan --help` and `sfdupes dwim --help` also list the
+  default excludes of the system they run on, and the filesystem types the walk
+  never records anything on.
 
 ### Duplicate detection
 

internal/sfdupes/cli.go

@@ -3,7 +3,6 @@
 package sfdupes
 
 import (
-	"bytes"
 	"context"
 	"errors"
 	"fmt"
@@ -177,32 +176,9 @@ func run(args []string, stdout, stderr io.Writer) int {
 	}
 
 	root := newRootCommand(stdout, stderr)
-
-	// Help that was asked for, with --help, -h or the help subcommand,
-	// goes to stdout. Execute returns no error after help, so helpErr
-	// keeps the one printHelp returns. Cobra's own help subcommand is
-	// replaced because it answers "sfdupes help scna" with the help of
-	// sfdupes.
-	var helpErr error
-
-	cobraHelp := root.HelpFunc()
-	root.SetHelpFunc(func(cmd *cobra.Command, _ []string) {
-		helpErr = printHelp(cmd, cmd.Flags().Args(), cobraHelp, stdout)
-	})
-	root.SetHelpCommand(&cobra.Command{
-		Use:   "help [command]",
-		Short: "Help about any command",
-		Run: func(_ *cobra.Command, names []string) {
-			helpErr = printHelp(root, names, cobraHelp, stdout)
-		},
-	})
-
 	root.SetArgs(args)
 
 	err := root.Execute()
-	if err == nil {
-		err = helpErr
-	}
 
 	var fatal fatalError
 
@@ -219,62 +195,14 @@ func run(args []string, stdout, stderr io.Writer) int {
 
 		return exitFatal
 	default:
-		// A usage error, which cobra or printHelp has already reported
-		// on stderr.
+		// A usage error, which cobra has already reported on stderr.
 		return exitUsage
 	}
 }
 
-// printHelp prints help that was asked for to stdout. It is the help of
-// cmd, or, for a command with subcommands, of the subcommand that
-// operands name: scan in "sfdupes help scan". Operands that name none,
-// as in "sfdupes help scna" or "sfdupes scna --help", are a usage
-// error, reported on stderr as for "sfdupes scna".
-//
-// cobraHelp is cobra's own help function. It prints to the command's
-// output writer, which is stderr, and drops a failed write. So the help
-// goes into a buffer first, and a failed write of the buffer to stdout
-// is a fatal error.
-func printHelp(
-	cmd *cobra.Command, operands []string,
-	cobraHelp func(*cobra.Command, []string), stdout io.Writer,
-) error {
-	if cmd.HasSubCommands() {
-		cmd, operands, _ = cmd.Find(operands)
-	}
-
-	// When the help subcommand runs instead of cmd, cobra has not yet
-	// added the --help flag that cmd's help and usage text list.
-	cmd.InitDefaultHelpFlag()
-
-	// Operands left over here name no subcommand. They are reported as
-	// cobra reports "sfdupes scna", which cobra.NoArgs rejects.
-	if cmd.HasSubCommands() && len(operands) > 0 {
-		err := cobra.NoArgs(cmd, operands)
-		cmd.PrintErrln(cmd.ErrPrefix(), err.Error())
-		cmd.Println(cmd.UsageString())
-
-		return err
-	}
-
-	out := cmd.OutOrStderr()
-	help := new(bytes.Buffer)
-	cmd.SetOut(help)
-	cobraHelp(cmd, nil)
-	cmd.SetOut(out)
-
-	_, err := stdout.Write(help.Bytes())
-	if err != nil {
-		return fatalError{err: fmt.Errorf("write stdout: %w", err)}
-	}
-
-	return nil
-}
-
 // newRootCommand builds the command tree. Everything on stdout is
-// machine-readable data, the version line included, or help that was
-// asked for, which run prints. The rest of the human-facing output
-// (usage, errors) goes to stderr.
+// machine-readable data, the version line included; all human-facing
+// output (help, usage, errors) goes to stderr.
 func newRootCommand(stdout, stderr io.Writer) *cobra.Command {
 	var showVersion bool
 
@@ -307,13 +235,11 @@ func newRootCommand(stdout, stderr io.Writer) *cobra.Command {
 			return errNoSubcommand
 		},
 	}
-	// Cobra prints the usage text of a usage error to the command's
-	// output writer, so that writer is stderr.
 	root.SetOut(stderr)
 	root.SetErr(stderr)
 	root.CompletionOptions.DisableDefaultCmd = true
 
-	// Cobra's built-in version flag prints to the output writer,
+	// Cobra's built-in version flag prints through the help writer,
 	// stderr; this one prints to stdout.
 	root.Flags().BoolVarP(&showVersion, "version", "v", false,
 		"print the version to stdout")

internal/sfdupes/cli_test.go

@@ -26,9 +26,6 @@ const usageMarker = "Usage:"
 // helpFlag asks for the help text.
 const helpFlag = "--help"
 
-// helpCommand is the subcommand that prints the help text.
-const helpCommand = "help"
-
 // workersFlag is the scan and dwim flag that sets the worker count.
 const workersFlag = "--workers"
 
@@ -628,14 +625,6 @@ func TestRunNamesDefaultDatabase(t *testing.T) {
 
 func TestRunUsageErrors(t *testing.T) {
 	// Usage errors keep exiting 2 with cobra's own report on stderr.
-	// An unknown subcommand is reported the same way with or without a
-	// request for help: the line naming it, then the usage text.
-	const (
-		unknown       = "nope"
-		unknownReport = "unknown command \"" + unknown +
-			"\" for \"sfdupes\"\n" + usageMarker
-	)
-
 	cases := map[string]struct {
 		args []string
 		want string
@@ -645,13 +634,7 @@ func TestRunUsageErrors(t *testing.T) {
 		"info with args":     {[]string{cmdInfo, "x"}, usageMarker},
 		"dwim with args":     {[]string{cmdDwim, "x"}, usageMarker},
 		"unknown flag":       {[]string{cmdScan, "--nope", "/"}, usageMarker},
-		"unknown subcommand": {[]string{unknown}, unknownReport},
-		"unknown subcommand with --help": {
-			[]string{unknown, helpFlag}, unknownReport,
-		},
-		"help for an unknown subcommand": {
-			[]string{helpCommand, unknown}, unknownReport,
-		},
+		"unknown subcommand": {[]string{"nope"}, "unknown command"},
 	}
 
 	for name, tc := range cases {
@@ -717,12 +700,9 @@ func TestRunScanRejectsWorkersBelowOne(t *testing.T) {
 func TestRunHelp(t *testing.T) {
 	t.Parallel()
 
-	// README §Settings: help goes to stdout, exits 0, and leaves stderr
+	// README §Settings: help goes to stderr, exits 0, and leaves stdout
 	// empty.
-	cases := [][]string{
-		{helpFlag}, {"-h"}, {helpCommand},
-		{cmdScan, helpFlag}, {helpCommand, cmdScan},
-	}
+	cases := [][]string{{helpFlag}, {"-h"}, {cmdScan, helpFlag}}
 
 	for _, args := range cases {
 		var stdout, stderr bytes.Buffer
@@ -732,20 +712,14 @@ func TestRunHelp(t *testing.T) {
 			t.Errorf("run(%v) = %d, want %d", args, code, exitOK)
 		}
 
-		if !strings.Contains(stdout.String(), usageMarker) {
-			t.Errorf("run(%v) stdout = %q, want the help text",
-				args, stdout.String())
+		if !strings.Contains(stderr.String(), usageMarker) {
+			t.Errorf("run(%v) stderr = %q, want the help text",
+				args, stderr.String())
 		}
 
-		// The help subcommand prints the same help as --help, which
-		// lists --help itself.
-		if !strings.Contains(stdout.String(), "-h, "+helpFlag) {
-			t.Errorf("run(%v) stdout = %q, want it to list %s",
-				args, stdout.String(), helpFlag)
-		}
-
-		if got := stderr.String(); got != "" {
-			t.Errorf("run(%v) stderr = %q, want nothing", args, got)
+		if got := stdout.String(); got != "" {
+			t.Errorf("run(%v) stdout = %q, want nothing (data only)",
+				args, got)
 		}
 
 		// README §Location: the help of sfdupes and of scan says where
@@ -755,9 +729,9 @@ func TestRunHelp(t *testing.T) {
 			"scan and dwim store", databaseEnv, rootDatabasePath,
 			stateHomeEnv, "~/.local/state", "not an absolute path is an error",
 		} {
-			if !strings.Contains(stdout.String(), want) {
-				t.Errorf("run(%v) stdout = %q, want it to name %q",
-					args, stdout.String(), want)
+			if !strings.Contains(stderr.String(), want) {
+				t.Errorf("run(%v) stderr = %q, want it to name %q",
+					args, stderr.String(), want)
 			}
 		}
 	}
@@ -767,48 +741,17 @@ func TestRunHelp(t *testing.T) {
 
 	run([]string{cmdScan, "-h"}, &stdout, &stderr)
 
-	if !strings.Contains(stdout.String(), excludeFlag+" PATH") {
-		t.Errorf("scan -h stdout = %q, want %s PATH", stdout.String(),
+	if !strings.Contains(stderr.String(), excludeFlag+" PATH") {
+		t.Errorf("scan -h stderr = %q, want %s PATH", stderr.String(),
 			excludeFlag)
 	}
 }
 
-func TestRunHelpScanPrintsScanHelp(t *testing.T) {
-	t.Parallel()
-
-	// "sfdupes help scan" and "sfdupes --help scan" print exactly what
-	// "sfdupes scan --help" prints: the help of scan, not of sfdupes.
-	var want bytes.Buffer
-
-	run([]string{cmdScan, helpFlag}, &want, io.Discard)
-
-	for _, args := range [][]string{
-		{helpCommand, cmdScan}, {helpFlag, cmdScan},
-	} {
-		var stdout, stderr bytes.Buffer
-
-		code := run(args, &stdout, &stderr)
-		if code != exitOK {
-			t.Errorf("run(%v) = %d, want %d", args, code, exitOK)
-		}
-
-		if got := stdout.String(); got != want.String() {
-			t.Errorf("run(%v) stdout = %q, want what scan %s prints, %q",
-				args, got, helpFlag, want.String())
-		}
-
-		if got := stderr.String(); got != "" {
-			t.Errorf("run(%v) stderr = %q, want nothing", args, got)
-		}
-	}
-}
-
 func TestRunScanUsageLine(t *testing.T) {
 	t.Parallel()
 
 	// README §Subcommands shows this usage line for scan, and the help
-	// and the usage error both print it. TestRunHelp and
-	// TestRunUsageErrors check which stream each goes to.
+	// and the usage error both print it.
 	const want = "\n  sfdupes scan [--workers N] [-x] [--no-default-excludes] " +
 		"[--exclude PATH]... PATH...\n"
 
@@ -821,13 +764,13 @@ func TestRunScanUsageLine(t *testing.T) {
 		t.Run(name, func(t *testing.T) {
 			t.Parallel()
 
-			var output bytes.Buffer
+			var stdout, stderr bytes.Buffer
 
-			run(args, &output, &output)
+			run(args, &stdout, &stderr)
 
-			if !strings.Contains(output.String(), want) {
-				t.Errorf("run(%v) output = %q, want the usage line %q",
-					args, output.String(), want)
+			if !strings.Contains(stderr.String(), want) {
+				t.Errorf("run(%v) stderr = %q, want the usage line %q",
+					args, stderr.String(), want)
 			}
 		})
 	}
@@ -893,9 +836,9 @@ func TestRunHelpDescribesOutput(t *testing.T) {
 		}
 
 		for _, want := range tc.want {
-			if !strings.Contains(stdout.String(), want) {
+			if !strings.Contains(stderr.String(), want) {
 				t.Errorf("run(%v) help lacks %q:\n%s",
-					args, want, stdout.String())
+					args, want, stderr.String())
 			}
 		}
 	}
@@ -979,32 +922,6 @@ func TestRunVersionWriteFailureIsFatal(t *testing.T) {
 	}
 }
 
-func TestRunHelpWriteFailureIsFatal(t *testing.T) {
-	t.Parallel()
-
-	// README §Error handling: a failed write to stdout is a fatal error,
-	// exit 1, reported on stderr starting with "sfdupes:". Help goes to
-	// stdout, so that holds for help too.
-	cases := [][]string{
-		{helpFlag}, {"-h"}, {helpCommand},
-		{cmdScan, helpFlag}, {helpCommand, cmdScan},
-	}
-
-	for _, args := range cases {
-		var stderr bytes.Buffer
-
-		code := run(args, failingWriter{}, &stderr)
-		if code != exitFatal {
-			t.Errorf("run(%v) = %d, want %d", args, code, exitFatal)
-		}
-
-		want := "sfdupes: write stdout: " + errWriteFailed.Error() + "\n"
-		if got := stderr.String(); got != want {
-			t.Errorf("run(%v) stderr = %q, want %q", args, got, want)
-		}
-	}
-}
-
 // scanFixture builds a small tree holding one duplicate pair and one
 // unreadable file and scans it into the database the caller has
 // pointed SFDUPES_DATABASE at. The unreadable file makes the scan warn

internal/sfdupes/dwim_test.go

@@ -190,21 +190,21 @@ func TestRunDwimHelpListsScanFlags(t *testing.T) {
 
 	run([]string{cmdDwim, "-h"}, &stdout, &stderr)
 
-	if !strings.Contains(stdout.String(), want) {
-		t.Errorf("dwim -h stdout = %q, want the usage line %q",
-			stdout.String(), want)
+	if !strings.Contains(stderr.String(), want) {
+		t.Errorf("dwim -h stderr = %q, want the usage line %q",
+			stderr.String(), want)
 	}
 
-	if !strings.Contains(stdout.String(), excludeFlag+" PATH") {
-		t.Errorf("dwim -h stdout = %q, want %s PATH", stdout.String(),
+	if !strings.Contains(stderr.String(), excludeFlag+" PATH") {
+		t.Errorf("dwim -h stderr = %q, want %s PATH", stderr.String(),
 			excludeFlag)
 	}
 
 	// README "Settings": the help lists the default excludes and the
 	// filesystem types the walk never records anything on.
 	help := strings.TrimSpace(defaultExcludesHelp(runtime.GOOS))
-	if !strings.Contains(stdout.String(), help) {
-		t.Errorf("dwim -h stdout = %q, want it to hold %q", stdout.String(),
+	if !strings.Contains(stderr.String(), help) {
+		t.Errorf("dwim -h stderr = %q, want it to hold %q", stderr.String(),
 			help)
 	}
 }

internal/sfdupes/exclude_test.go

@@ -196,8 +196,8 @@ func TestDefaultExcludesHelp(t *testing.T) {
 	run([]string{cmdScan, "-h"}, &stdout, &stderr)
 
 	help := strings.TrimSpace(defaultExcludesHelp(runtime.GOOS))
-	if !strings.Contains(stdout.String(), help) {
-		t.Errorf("scan --help = %q, want it to hold %q", stdout.String(), help)
+	if !strings.Contains(stderr.String(), help) {
+		t.Errorf("scan --help = %q, want it to hold %q", stderr.String(), help)
 	}
 }